COMMD1 forms oligomeric complexes targeted to the endocytic membranes via specific interactions with phosphatidylinositol 4,5-bisphosphate.
Copper metabolism Murr1 domain 1 (COMMD1) is a 21-kDa protein involved in copper export from the liver, NF-kappaB signaling, HIV infection, and sodium transport. The precise function of COMMD and the mechanism through which COMMD1 performs its multiple roles are not understood. Recombinant COMMD1 is a soluble protein, yet in cells COMMD1 is largely seen as targeted to cellular membranes. Using co-localization with organelle markers and cell fractionation, we determined that COMMD1 is located in the vesicles of the endocytic pathway, whereas little COMMD1 is detected in either the trans-Golgi network or lysosomes. The mechanism of COMMD1 recruitment to cell membranes was investigated using lipid-spotted arrays and liposomes. COMMD1 specifically binds phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) in the absence of other proteins and does not bind structural lipids; the phosphorylation of PtdIns at position 4 is essential for COMMD1 binding. Proteolytic sensitivity and molecular modeling experiments identified two distinct domains in the structure of COMMD1. The C-terminal domain appears sufficient for lipid binding, because both the full-length and C-terminal domain proteins bind to PtdIns(4,5)P2. In native conditions, endogenous COMMD1 forms large oligomeric complexes both in the cytosol and at the membrane; interaction with PtdIns(4,5)P2 increases the stability of oligomers. Altogether, our results suggest that COMMD1 is a scaffold protein in a distinct sub-compartment of endocytic pathway and offer first clues to its role as a regulator of structurally unrelated membrane transporters.
Burkhead
Jason L
JL
Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239.
Morgan
Clinton T
CT
Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239.
Shinde
Ujwal
U
Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239.
Haddock
Gabrielle
G
Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239.
Lutsenko
Svetlana
S
Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239. Electronic address: lutsenko@ohsu.edu.
D048868:Adaptor Proteins, Signal Transducing; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D003300:Copper / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D011485:Protein Binding / Q000502:physiology; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D022161:Transport Vesicles / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C480519:COMMD1 protein, human; D002352:Carrier Proteins; D046912:Multiprotein Complexes; D016328:NF-kappa B; D019269:Phosphatidylinositol 4,5-Diphosphate; D003300:Copper